Extension grate for multiple retort stokers



March 29, 1955 w R|DDEL| 2,704,984

EXTENSION GRATE FOR MULTIPLE RETORT STOKERS Filed July 7, 1954 Q I T- 1-M- INVENTOR.

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United States Patent EXTENSION GRATE FOR MULTIPLE RETORT STOKERS Wi liam A. Riddell, Frederick, Md.

Application July 7, 1954, Serial No. 441,726

5 Claims. (Cl. 110-33) This invention relates generally to furnace grates and more particularly to extension grates for underfeed multiple retort stokers.

Ordinary multiple retort underfeed stokers all have movable extension grates, in which the bars are fixed and immovable. The bars or grates frequently burn out when they become plugged with molten or semi-molten ash or clinker. When this happens it is usually necessary to replace the entire grate. In other types of stokers where grate bars are movable and positively actuated other problems present themselves, such as difliculty of grate bar replacement and various mechanical and operational considerations.

With these problems in mind the primary object of my invention is to provide an improved extension grate for stokers or the like which has sections which are relatively movable so as to prevent hot ashes, generally semimelted or melted, from caking on the grate or clogging the same and thus rendering the grate adapted for extended usage without burning out.

More specifically the object is to provide an extension grate for a multiple retort stoker in which upper and lower series of grate bars are loosely mounted in a reciprocating carriage, and in which the grate sections or bars while supporting the fuel bed may independently move in response to fluctuations in applied pressures or resistance over various areas so as to give to the entire fuel supporting surface an irregular weaving action. This weaving action in turn opens up draft apertures through the fuel bed to prevent clogging and increases air circulation through the grate to keep it at cooler temperature and preserve the grate bars from burning out.

A further object is to provide a multi-section grate construction for use in a multiple retort stoker, in which the upper and lower grate bars or sections are swingably interconnected to permit of the aforesaid weaving action therebetween, without the need of direct pivotal fastener connections between the sections, and in which the grate sections are so formed that they can be removed merely by lifting out of position thus greatly facilitating the replacement and installation operation.

With these objects in view, my invention broadly comprises the provision of a multi-section extension grate with the sections or grate bars providing a single continuous inclined fuel supporting surface, said sections being independently swingable about transverse parallel axes for separate movements therebetween to cause a flexing of said surface, and said sections being loosely interlocked to permit independent swinging movement of all the sections. The grate sections are pivotally associated with a supporting frame and are so arranged with respect thereto as to be allowed only limited movement about their respective pivot axes.

The above mentioned and other objects of the present invention will be referred to in the following specification, reference being made to the accompanying drawings, in which Fig. 1 is a longitudinal vertical section taken substantially along the longitudinal center line of a retort of a multiple retort underfeed stoker in which my improved movable extension grate construction is employed. The view is only fragmentary of the stoker and shows only the extension grate and its mounting means with closely associated parts of the stoker. Here the grate is shown in its normally straight or unflexed condition.

Fig. 2 is similar to Fig. 1 with the grate sections swung ice slightly about their respective axes and with the extension grate in a broken or flexed condition.

Fig. 3 is a section on the line 33 in Fig. 2 showing how adjacent grate bar sections of a group may assume separate self-adjusted positions.

Referring now more particularly to the drawing, reference numerals will be used to denote like parts and structural features in the different views. As heretofore mentioned, only the grate portion of an underfeed stoker, designated generally at 10, is shown in the drawing, the other parts of the stoker being of conventional multiple retort construction and not being involved in the present invention. For a clear understanding of the disposal of the grate mechanism in the stoker construction it should suflice to explain that the stoker fuel is moved from the retorts or hopper, as by a reciprocating pusher, forwardly over the delivery shelf 11 and onto the grate, which has been designated generally by the numeral 12. The fuel then moves slowly down the inclined grate as a burning fuel bed with the completely incinerated ashes thereof falling from the lower edge of the grate into an ash pit (not shown).

The stoker 10 has transversely spaced bracket means 13 on its frame which slidably support a pair of side plates 14. These plates are interconnected by transverse tie members 20, 22 and 25 so as to jointly form a carriage for the grate 12, which carriage has a limited amount of fore and aft sliding movement with respect to the stoker proper as indicated by the dotted lines in Fig. l. Grate 12 is comprised of upper and lower grate sections designated at 15 and 16, respectively, and which are constructed and mounted on the slidable grate carriage in a manner now to be described.

Each grate section includes a plurality of transversely spaced longitudinally extending grate bars 17. The side by side arrangement of such bars in an extension is indicated in Fig. 3. Round and slightly tapered lugs or projections 18 extend laterally from the bars and into the spaces therebetween. It will be noted that these projections are many in number and that they serve to allow passage of air upwardly through the grate in the direction indicated by the arrow A.

The grate bars 17 of the upper section 15 are down wardly flanged, as at 19, and each of these flanges is provided with a hook 19 These hooks are adapted to engage over and seat on a spacer pipe 20a about the cross bar 20 which extends between and connects the side plates 14 so that the hooks and their carried section 15 are allowed a limited amount of swinging movement about the axis of bar 20.

The lower grate section 16 has a similar transverse construction to that of the section 15, with longitudinally extending grate bars 17 having the lateral projection 18, and with the bars 17 relatively movable as in the upper construction. This section is provided with one or more hook type mounts 21 which engage the cross bar 22 having a fulcrum tip 23 on which the hook members 21 are loosely hung.

In the upper section, 15, the upper ends of the bars 17 are formed with a rearwardly and downwardly projecting hook 24. The transversely extending cross bar 25 has a recess 25a for engagement by the hooks 24, and is connected to the forward end of an actuator bar 26 power actuated for fore and aft movement to slowly reciprocate the entire carriage.

Attention is now directed to the split in the grate or the contacting surfaces between the sections 15 and 16. The lower end edges of the bars 17 in the upper section angle rearwardly and downwardly as at 27. The flange plate 19 projects downwardly beyond the bars 27 as at 28. The upper edge of the lower grate section 16 is formed to normally fit flush against and interlock with the lower edge of section 15, as in Fig. 1. To insure this the upper edges of the bars 17 in section 16 angle rearwardly and downwardly, as at 29, so as to be in flush engagement with the edges 27 of the upper section. Plate or flange 21 is then cut away as at 30 to allow projection 28 to extend below the upper ends of the grate bars in the lower section. It will be understood that the flange plates 19 are in the same general vertical plane with flange plates 21 and bars 17 in the section 16.

In normal operation the fuel is fed in over the shelf 11 and moves down over the inclined grate section in a continuously burning bed while the actuator bar 26 is slowly reciprocated to move the entire carriage forth and back. Preferably adjacent carriages are alternately reciprocated.

When the carriage moves forwardly the upper and lower grate sections will normally assume their properly flush and aligned positions as indicated in Fig. 1, and, under perfect fuel buring conditions will probably retain such normally aligned relationship on the return or back movement.

Perfect combustion seldom exists over any appreciable length of time, however, due to fluctuations in fuel content and distribution, and other variables, with a result that uneven combustion, formation of clinkers, air pockets, and ultimate burning out of grate sections results.

The frequent necessity for replacement of grate bars is here eliminated, or greatly reduced, as exhaustive tests of the present invention have established, because the adhesion of clinkers, the variations in fuel weight, etc. will cause the grate bars to tilt and fluctuate to produce the highly desirable weaving action heretofore referred to. This action in turn releases the clinkers, agitates the fuel to cover up air holes, and otherwise renders the combustion bed more uniform, and thereby prevents excessive localizing of excessive temperature application to any grate bar areas.

It will be understood that the longitudinal weaving action wherein section 15 tilts forwardly and downwardly and section 16 moves upwardly and rearwardly about their respective pivots will be limited by the contact be tween the undersurface 31 of the shelf 11 and the upper surfaces 32 of the bars 17 in the section 15. On the other hand, weaving action in a grate heaving direction, as shown in Fig. 2, is limited by contact between the surface 33 of the stoker frame and the bottom edge surfaces 34 of the grate bars 17 in the lower section 16.

An important feature of the invention lies in the fact that the grate sections 15 and 16 are loosely interlocked, to allow the weaving action, without the necessity of connecting pins or bolts. By providing the fitting offsets in the adjacent edges of the sections, swinging movement of one section causes swinging of the other and the sections are retained against improper displacement. Furthermore, as the grate bars are merely hung in place, it is a relatively simple matter to replace them if and when required, it only being necessary to lift off the shelf plate 11 to free the upper grate bars.

The air for combustion moves through the air chamber and upwardly through the grate bars in the general direction indicated by the arrow A. The multiplicity of round projections 18 allow the air to pass in all directions for most eflicient combustion even though a part of the area of the grate may become temporarily plugged up with ashes or clinkers. This construction plus the heretofore discussed weaving or flexing of the grate to prohibit clogging and excessive localized temperatures assures most effective air cooling of the grate bars to prevent their burning out.

I have accordingly provided a new and improved extension grate construction which effectively and economically carries out the aforementioned objectives. It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

1. In a multiple retort stoker, an extension grate comprising upper and lower series of inclined grate bars normally disposed in end to end alignment to form a continuous fuel supporting surface, transversely disposed pivot forming support bars disposed one under each series of grate bars and supporting such grate bars for independcut tilting movement, and interlocking connections between the adjacent ends of said grate bars whereby the tilting of one bar in either direction about its support bar will oppositely tilt the normally aligned grate bar about the support bar upon which it is supported, all of said grate bars being independently and loosely mounted whereby the entire fuel supporting surface of the grate may have a free self-adjusting action under the fuel bed moving downwardly thereover.

2. In a stoker, a frame mounted for fore and aft movement and including a pair of suspension members disposed crosswise of the frame in fore and aft positions, a pair of inclined grate sections mounted one on each suspension member and meeting endwise to normally form a continuous inclined fuel supporting surface, each grate section comprising a transverse series of independent grate bars each having a hook portion engaging downwardly over the suspension member below it allowing oscillation of each grate bar about the suspension member independently of the other grate bars in the series, each grate bar being in longitudinal alignment with a corresponding grate bar in the other section and having its adjacent end configured to interlock therewith whereby tilting movement of any grate bar in either direction about its axis will cause tilting movement of its corresponding aligned grate bar in the opposite direction about its axis.

3. In a stoker, a frame supported for fore and aft reciprocating movement and including a pair of suspension members mounted crosswise of the frame in fore and aft positions, a pair of upper and lower grate sections mounted one over each suspension member and meeting endwise to jointly form a normally continuous inclined fuel supporting surface, each grate section comprising a transverse series of independent grate bars each having a hook portion engaging downwardly over the suspension member below it and allowing oscillation of each grate bar about the axis of the suspension member independently of the other grate bars in the series, each grate bar being in longitudinal alignment with a corresponding grate bar in the other section and having their adjacent ends configured to endwise interlock whereby tilting movement of any grate bar in either direction about its axis will cause tilting movement of its corresponding aligned grate bar in the opposite direction about its axis, the hook portions of the grate bars of the upper grate section only partially encompassing the suspension member which they engage so as to permit limited endwise movement of such bars with respect to the aligned grate bars of the lower section.

t. In a stoker, a carriage mounted for fore and aft rec1procating movement and having a pair of spaced suspension bars extending crosswise thereof, a pair of inclined grate sections disposed one over each of the suspension bars and in normal alignment with each other to form a continuous fuel supporting surface, each of the grate sections comprising a series of parallel adjacent grate bars each of which has a depending hook portion engaging over the suspension bar below it to support the grate bar thereon for tilting movement independently of every other grate bar in the series, and the hook portions of the upper grate bars opening downwardly and forwardly so as to give each grate bar of the upper section freedom for limited sliding movement on the suspension bar in a direction lengthwise of the grate bar and independently of the other grate bars in the section.

5. The structure defined in claim 4 and in which opposed side faces of the adjacent grate bars of each grate section are provided with profusely distributed laterally pro ecting spaced lugs defining passageways for the passage of air for combustion used to cool the grate bars.

References Cited in the file of this patent UNITED STATES PATENTS 1,282,346 Wilson Oct. 22, 1918 1,578,701 Aram Mar. 30, 1926 1,978,106 Harrison Oct. 23, 1934 

